Introduction to API Specification 2C. 6 th Edition vs. 7 th Edition

Transcription

1 Introduction to API Specification 2C 6 th Edition vs. 7 th Edition

2 Goals of API Spec 2C 7 th Edition Address gross overload/supply boat entanglement issue Incorporate all types of offshore cranes, including: Construction Derrick Barges Pipe Lay Vessels Support Vessels Shipboard Cranes Knuckle Boom Cranes Provide design requirements for new crane uses without significantly affecting cranes currently covered by previous editions Differentiate between crane designs based on intensity or frequency of use

3 Significant Changes from 6 th Edition Gross overload / supply boat entanglement Duty cycle consideration (frequency / intensity of use) Wire rope design factors Structural design factors

4 Background API Spec 2C 6 th Edition and European standard EN and -2 both published 2004 addressing offshore crane sizing and safety requirements API Spec 2C 6 th Edition Focused on cranes for oil production and drilling facilities Safety based on structural design and integrity Increased safety factors are emphasized above instrumentation / gadgets as a means of providing safe cranes EN Covers cranes for all offshore applications Safety focused on instrumentation / gadgets instead of increased safety factors Main requirement is an Automatic Overload Protection System (AOPS) that takes control away from the operator and releases the brakes while over the supply boat

5 Background API Spec 2C 7 th Edition drafted to incorporate additional crane uses, expanding on previous versions and maintaining safe operations as governing theme Designed as a superior international standard for offshore cranes based on more realistic criteria and more definitive guidance

6 Gross Overload Conditions / Failure Mode Assessment API 6 th Edition Did not specifically address Gross overload conditions Failure mode calculations only required upon request of purchaser API 7 th Edition Addresses gross overload using failure mode assessment Requires failure mode results to be provided to the customer Protects the crane operator in the event of an unbounded gross overload (supply boat entanglement) If failure mode cannot be met, gross overload protection system (GOPS) required to assure that structure holding the operator does not fail in the event of a gross overload No AOPS required

7 Supply Boat Entanglement Causing Gross Overload Not to be confused with exceeding the SWL of the crane

8 Gross Overload Conditions (From Supply Boat Entanglement) EN Seems to consider supply boat entanglement to be a common event Damage to equipment unacceptable in catastrophic events Accomplished through Automatic Overload Protection System (AOPS) which senses an overload and releases the load AOPS creates increased risk of malfunction and dropped loads API 7 th Edition Considers supply boat entanglement an extremely rare but serious event with special attention required Equipment damage considered acceptable in this rare catastrophic event Accomplished through failure mode assessment showing structure holding operator s cabin will not be first to fail in any condition Considers hazards created by AOPS to be worse than the potential benefits

9 Pitfalls of AOPS AOPS requirements over emphasize protection of replaceable components/machinery to the extent of creating additional hazards to personnel. Examples of additional personnel hazards Holds loads over supply boat personnel with brakes intentionally disabled Loads supported only by retention or containment of hydraulic oil pressure Can and have inadvertently dropped loads on supply boat Complexity of components adds to number of parts that must be maintained, inspected, and tested Numerous components increase likelihood of failure Creates a false sense of security

10 Example of Failure Assessment (From Supply Boat Entanglement) 800, , ,000 Pedestal Suspension Boom Main Rope Gantry Failure Load (lb) 500, , , , , Working Radius (ft)

11 Example of Failure Assessment (From Supply Boat Entanglement) 800, , ,000 Pedestal Minimum Failure Offboard SWL Failure Load (lb) 500, , , , , Working Radius (ft)

12 Example of Supply Boat Entanglement Crane on semi-submersible subjected to event while handling anchors Instantaneous overload in excess of 200% SWL Wire rope pulled off the hoist drum, hydraulic motor destroyed due to overspeed No personnel injuries Crane returned to service following replacement of wire rope and hydraulic motor Outcome acceptable under API 7 th Edition but not EN 13852

13 Structural Fatigue API 6 th Edition Structural fatigue requirement is 25,000 cycles at 133% of max SWL Crane structures expected to last years * EN and ISO assume machinery and structures have same useful life API 7 th Edition Structural fatigue requirement is 1,000,000 cycles at 50% onboard SWL Equivalent fatigue damage of 6 th Edition Differentiates between structures and machinery* Crane structures expected to last at least years

14 Machinery and Wire Rope Duty Cycle API 6 th Edition Did not address duty cycle, only structural fatigue * EN and ISO assume machinery and structures have same useful life API 7 th Edition Differentiates between structures and machinery* Machinery expected to last 5 years before major overhaul / replacement API machinery is replaced or overhauled multiple times before crane structure is retired Duty classifications based on actual historical crane usage data

15 Duty Classifications Examples Production Duty Construction Duty Intermediate Duty Drilling Duty

16 Crane Duty Classifications Crane Duty Cycle Classification Production Duty Typical Annual Operating Hours 200 Typical Applications Offshore cranes on fixed production platforms Construction Duty Intermediate Duty Drilling Duty ,000 5,000 Offshore cranes on barges or vessels, heavy lift cranes Offshore cranes on fixed or floating platforms with temporary rigs or intermittent periods of intensive use Offshore cranes on MODUs or floating production facilities with full-time, heavy-use drilling operations Note: Where possible, purchaser specified data used in place of duty classifications

17 Historical Crane Usage Data Year Usage (Hours) Drilling Contractor Data: (based on logs & engine hours) Average of Jackups-Primary Crane Max of Jackups-Primary Crane No. of Primary Cranes Average of Semi/DrillShips-Primary Crane Max of Semi/DrillShips-Primary Crane No. of Primary Cranes Production Platform Data #1: (based on Engine Hours) Average of Platform Cranes w/o Drilling Max of Platform Cranes w/o Drilling No. of Cranes Production Platform Data #2: (based on Hoist Hour Meters) Average of Platform Cranes w/o Drilling Max of Platform Cranes w/o Drilling No. of Cranes Floating Production / Drilling Systems: Spars/TLP with Drilling Rig (4) Spars/TLP w/o Rig (1) Ave / Max 2315 / 5000 engine hr/yr 650 engine hr/yr

18 Wire Rope Design Factors API 6 th Edition Fixed design factor of 5 for running rigging without reeving efficiency Fixed design factor of 4 for standing rigging Impractical for larger cranes, such as construction cranes and derrick barges * Certifying authorities for larger cranes use design factor of 3 for lifts over 160 tons and account for reeving efficiency API 7 th Edition Little to no effect on cranes covered by API 6 th Edition Sliding factor based on SWL that allows larger cranes lower factors in line with industry practice* Reeving efficiency now considered due to high number of parts of line required for larger construction cranes Higher capacity cranes, such as derrick barges, have similar factors to current certifying authorities

19 Wire Rope Design Factors 6 API 6 th Edition 5 Design Factor 4 API 7th Edition API 6th Edition Note: API 7 th Edition, EN , DNV and Lloyds curves are all overlapping EN DNV Lloyds , , , , , , , ,000 SWL (lb)

20 Structural Design Factors EN Uses same factor of safety for pedestal / slew bearing as the rest of the crane structure No additional factor on the pedestal / slew bearing API 7 th Edition Uses higher factor of safety for pedestal / slew bearing compared to the rest of the crane structure Significant additional factor of safety applied to the pedestal / slew bearing to help ensure that the main crane structure and operator remain attached to the platform in a catastrophic event

21 Structural Design Factors API 6 th Edition Minimum onboard dynamic coefficient (Cv) of 1.33 Additional Pedestal factor of 1.5 Impractical for large construction cranes, derrick barges or shipboard cranes in calm waters * Certifying authorities use approximately 1.1 for Cv for lifts over 160 tons and many do not use a pedestal factor API 7 th Edition Little to no effect on cranes currently covered by API 6 th Edition Sliding minimum onboard dynamic coefficient from 1.33 to 1.1 based on SWL Additional sliding pedestal factor from 1.5 to 1.2 based on SWL Offboard dynamic coefficients for typical oil production cranes have not changed Higher capacity cranes, such as derrick barges, have similar factors to current certifying authorities

22 API 7 th Edition Structural Design Factors Onboard Cv Pedestal Factor Factor , , , , , , , ,000 SWL (lb)

23 Minimum Hook Velocity API 6 th Edition Calculations given but was not mandatory Minimum hook velocity of 20 ft/min at 0 ft significant wave height API 7 th Edition Mandatory for all offboard ratings If not met, load chart cannot be provided for the specific conditions Minimum hook velocity of 2 ft/min at 0 ft significant wave height Above 6 ft significant wave height minimum hook velocity is the same as the 6 th Edition

24 Minimum Hook Velocity 100 Hook Velocity (ft/min) API 6th API 7th EN Significant Wave Height (ft)

25 Other Changes Cylinder design factors updated to include dynamic load factor Cv Hoist section updated to require separate dynamic and static brakes Load/moment indicators required on intermediate, drilling, and construction duty cranes Personnel capacity increased to 50% of SWL as opposed to 33% of SWL to more adequately align with OSHA and other standards and simplify ratings Align noise requirements with OSHA

26 Other Changes Material requirements clarified and aligned throughout the standard Minimum toughness (Charpy) requirements provided instead of relying on crane manufacturer to determine ductility requirements Example calculations updated to reflect changes Default Dynamic Method (fixed Cv of 2.0) renamed Legacy Dynamic Method to discourage use Drastically reduced number of references to external standards for ease of use internationally

27 Summary API 7 th Edition is a viable international standard incorporating all offshore crane applications Failure mode calculations/gops ensure operator safety without increasing the risk of dropping the load In the rare event of supply boat entanglement, injury to personnel is prevented Cranes covered by the 6 th Edition essentially unchanged while higher capacity cranes use similar to factors used by certifying authorities Entire standard reviewed and updated to match current technology and practice

28 Summary API 7 th Edition provides definitive technical guidance and unambiguous design rules to ensure cranes are designed to safely operate in the challenging offshore environment Cranes designed to API 2C 7 th Edition provide a superior balance of safety and simplicity